Innovative application of ultrasonic mixing to produce homogeneously mixed nanoparticulate-epoxy composite of improved physical properties

An innovative ultrasonic dual mixing process (ultrasonic mixing along with impeller stirring) has been employed to disperse round Al2O3 (<25 nm) particles in epoxy resin. Characterization of the nanoparticulate-epoxy composite has been carried out using TEM, AFM, DTA, TGA and FTIR and compared with the results obtained in epoxy without particles. When epoxy is treated by this dual mixing there is formation of self organized hexagonally arranged lattice of nano-sized cavities at 40% and 55% amplitudes, increasing its glass transition temperature. When nanoparticles are dispersed in epoxy, the arrangement of cavity appears somewhat disturbed compared to those arrangements of cavities in epoxy without particles. While mixing by stirring results in agglomerated particle clusters where several particles touch each other, use of ultrasonic dual mixing results in linear clusters where the distance between particles increases and the size of cluster decreases with increasing amplitude. Nanoparticulate-epoxy composite processed by dual mixing at amplitude of 55% shows the best results in terms of improvement of glass transition temperature and thermal stability, which improves further with increasing particle content. It has been attributed to the bonding of epoxide group in epoxy resin with the free OH groups present on the nanoparticle surface by hydrogen bonding, which is more extensive under UDM, particularly at high amplitude of 55%, constraining the movement of polymer chain.